Process of making roads



Patented any ac, iaae.

PTEWT (EFFECT.

CHARLTON WILDELR, OF CINCINNATI, OHIO, ASSIGNOR TO THE CROWN ROCK ASPHALT COMPANY, OF CINCINNATI, OHIO, A CORPORATION OF OHIO.

PROCESS OLE MAKING ROADS.

No Drawing.

My invention relates to a process'of preparing, shipping and laying rock asphalt. The invention herein described is adapted to be practiced on any rock asphalt, but the times, temperatures and other conditions are disclosed herein With particular reference to the treatment of rock asphalt from Grayson County, Kentucky. This asphalt averages approximately 5.65 percent bitumen and the mineral aggregate is sharp, hard and graded sand analyzing 98.27 percent silica. There is also present from to 4 of one percent moisture.

There is very little exact or dependable chemical information concerning bituminous substances and particularly rock asphalt. Asphalts are supposed to be of petrolic origin and contain a great variety of hydrocarbons of numerous difierent series and a wide range of molecular weights. Some of these hydrocarbons are aliphatic, some aromatic, some saturated and some unsaturated. The bituminous content of natu* ral rock asphalt is supposed to differ from that of asphalt such as Trinidad Lake asphalt, in that more unsaturated hydrocarbons are present. Because of this paucity of exact information the chemical or physical actions and reactions which either take place or are prevented by this particular process can only be expressed by reference to their manifestations, that is, by the change in color or physical condition of the product which has been found to be critically significant in many cases including the present instance. When the rock asphalt is mined it is of a gray or brown color, or gray brown color. The particles of the rock asphalt do not adhere readily together just after being mined and the material can be handled with a shovel or with other ordinary implements. After it has been placed on the road however and subjected to the action of the sunlight which seems to be peculiarly catalytic in effect, the gray or brown, or gray brown color changes to a bright black. The particles of material then adhere securely together. Otherwise expressed, the material seems to set up as it changes color. In this latter condition the asphalt is very hard and cannot be readily handled or shipped.

It is desirable for road building purposes Serial No. 40,451.

that the asphalt used contain approximately 7 percent bitumen. lin order to meet these requirements it is necessary either to discard a large percentage of the rock asphalt mined, or to fortify it with additional asphaltfor bitumen.

A suitable bituminous fortifying agent is Trinidad Lake asphalt. 1F rom 8 to 10 ercent in quantity of Trinidad Lake aspha t is cut back with the oil flux of an asphaltic base petroleum, Said oil flux having a penetration of from 300 to 350. However, any asphaltic. or bituminous material can be used, the advantage of the Trinidad being that it has incorporated therewith colloidal dust and is otherwise of hard quality adapted to raise the general average hardness of the bitumen of the resulting product.

In view of the soft nature of the bitumen of the rock asphalt, this fortifyin with a harder grade is often desirable. fiowever, it has generally been regarded as impossible to get a hard grade of bitumen or in fact anything other than an oil to mix with the rock asphalt as mined, without the application of heat to make it more fluid.

Heretofore it. has been considered essential, indeed it was the invariable practice in the art, to either employ such relatively high temperatures in connection with the mixing treatment, or else to continue the heat application during the mixing to a point where the asphaltic rock changed from its gray or gray brown color characteristic of the crude mined product to the bright black color characteristic of the finished or ultimate product. Tn consequence of this completion of the cooking incidental to the mixing operation as heretofore carried on in practice, the asphaltic rock reached the set up or hard agglomerate and solidified mass condition at the comple tion of the mixing stage and this refractory material necessarily had to be physically or mechanically reduced or broken up at a great expense and with some loss in order to restore the set up material to the loose or fluctuant physical state suitable for ship ment manipulation or for road application. This economic Waste and physical disadvantage has been a long reco ized and familiar problem in the art, which has heretofore been regarded as inherent in and inevitably incident to the nature oil the material when subjected to the requisite mixing and heat treating operations Attempts have been made to render the set up rock asphalt shipable by mining with it a quantity of volatile oil adapted to takeaway the rock-like properties of the mass. in theory the volatile oil evaporates after the rock asphalt is laid but in prac tice it does not entirely disappear, particularly from the base of the road GOZISW quently rock asphalt so prepared for shipment produces roads of interior strength and quality accompanied bya very undesirable road mobility,

My process supplies a definite and satisfactory solution oi this difiiculty in providing a suitably fortified asphaltic rock which at the end of the mimng stage is in a physical state and condition most advantageous for handling, shipping and manipulation, by reason or its meal-like relatively pulverulent mass, or unset-up state. lln other words, the material produced by my process is in effect a new material in the industrial or economical sense,.i. e., a raw but fortified, unset-up asphaltic rock isting in a more or less disintegrated. physical state suitable for both shipment and road application manipulations. This raw or unconditioned material is converted from this state to its finished product or set-up state either by secondary heat treatment after shipment or by sun exposure alter road application 'lhe object of my invention is to provide a process for making roads of hard uniform quality and up to specifications out of natural rock asphalt, the bituminous content 0]? which is below specifications;

Another object or my invention is to pro vide a process for fortifying natural. roclr asphalt with additional asphaltic or bituminous binder without impairing the characteristics of the material from view point shipping e After the natural rock asphalt is mined is ground up into a rock meal of such fineness that most of it will pass through. a quarter inch screen ll hammer reducing mill is very suitable tor this operation, Next, samples talren determine the exact bituminous content of the rock meal in order to calculate how much must be Eon titled The material is then passed into a revolving drum heated by an oil burner where it is kept, for approximately two minutes. It emerges from this drum at a temperature of to 150 lt is next put into a mixer where the bituminous ion tifying element is added, The mixer is preferably oil the double shaft and paddle type: The iortifying bitumen is introduced at a temperature of :lrom 200 to 250 H2, and the entire mass is mixed from oneto two panacea minutes. The 100 to 150 of temperature of the roclr asphalt is not sufficient to cause the change chemical or physical which is manifested by the change of color and the setting up oi the mass, yet the temperature is sulficient to prevent undue chilling of the lortilying bitumen which is introduced,

The temperature of from 200 to 250 is ade-- quate to make the lortilying bitumen sufliciently fluid to mix readily, but the per centage of bitumen being in the neighbor hood of two percent-of the total mass, at the most, is not suiiicient in quantity to raise the temgerature of the entire mass to such a degree that the roclr asphalt changes color and condition,

After this mining operation, the resulting material is placed in storage piles. lt can be handled with shovels and by ordinary methods tor shipping, and does not need to be dynamited out of the storage pile as v would be necessary had the color changed. Alter shipment it is laid cold upon the road and raked rolled in the usual manner. lt should preferably be laid in warm dry weather and the suns heat light is suiiicient to cause the laid roclr asphalt change color, set up and form into a soil); mass right on the road. lloclr asphalt usu ually continues this setting up process over some period of time-often two or three years, A. oartial change is advisable before opening tile road to trafic. This partial change or setting up should preferably place before rolling and the greater its degree the less danger will there of early trafic injuring the road,

'ln practicing this process the times, tern peratures proportions herein. disclosed may be varied according to exact ture of the rock asphat, the moisture it contains, the quality or its bituminous binder, the size of the mineral aggregate and the exact nature or the bituminous ion til ying material, From the above disclosure however the process be readily applied by those skilled in the art to all grades roclr asphalt and I desire to be limited only by the ensuing claims:

Having described my invention, 1 claim: a

l. The process of making roads out of natural roclr asphalt, the bituminous content of which. is below specifications, comprising the steps of grinding up the natural roclr asphalt, heating the same to a temperature of between 100 and 150 l1, adding thereto and. mixing therewith a predetermined quantity of fortifying bituminous material heated to from 200 to 250 F, applyi the resulting material in cold condition to the road to be paved, and exposing the same to action oil the sunlight to harden it into a solid mass.

2, The process of iortiilying natural rock asphalt with. bituminous material comp-ising the steps of grinding the rock asphalt, heating the same to a degree suficiently hot not to chill unduly the fortifying bitumen and yet not hot enought to cause the mass to set up, adding to and mixing therewith fortifying bitumen heated to a degree sufficient to render the same fluid, and yet not sufficiently hot to cause the bitumen of the rock asphalt to set up.

8. The process of fortifying natural rock asphalt with bituminous material without injuring the shipping qualities of the product comprising the step of -m1xing the natural rock asphalt with the fortifying bituminous material, the temperature of the fortifying bituminous material being such that it is sufiiciently fluid to mix readily with the rock asphalt, the temperature of the rock asphalt being such that it will not chill the bituminous material to an extent sufiicient to prevent the mixing therewith, the tem 'perature of the entire mass being such that the bituminuous binder thereof will not set up and cause the rock asphalt to form a solid rock like mass.

4. The process of fortitying natural rock asphalt with bituminous material compris ing the step of mixing the natural rock asphalt with the fortifying bituminous material, the temperature of the fortifying bituminous material being between 200 and 250 F, and the temperature of the rock asphalt being between 100 and 150 F.

5. The process of making roads out of natural rock asphalt, the bituminous content of Which is below specifications comprising the steps of grinding up the natural rock asphalt, heating the same to a temperature slightly below that at which the particular grade of rock asphalt changes in color from gray or brown to black, adding thereto and mixing therewith a predetermined quantity of bituminous material heated to a temperature at which it is suficiently fluid to mix with the rock asphalt, and applying the resulting gray or brown material in cold condition to the road to be paved, and exposing the same to action of the sunlight preparatory to opening the road to trafiic.

my name.

CHARLTON WILDER.

- In witness whereof, I hereunto subscribe 50 

